private void setWinner() {
    if (checkWinner(XCHAR))
      winner = XCHAR;
    else if (checkWinner(OCHAR))
      winner = OCHAR;
    else if (countMoves() == boardSize * boardSize)
      winner = DRAWCHAR;
    else
      winner = EMPTYCHAR;
  }

  private int countMoves() {
    int count = 0;
    for (int i = 0; i < boardSize; i++)
      for (int j = 0; j < boardSize; j++)
        if (board[i][j] != EMPTYCHAR)
          count++;
    return count;
  }

  private boolean checkWinner(int c) {
    if (checkMainDiag(c))
      return true;
    if (checkOtherDiag(c))
      return true;
    for (int i = 0; i < boardSize; i++) {
      if (checkWinnerRow(i, c))
        return true;
      if (checkWinnerCol(i, c))
        return true;
    }
    return false;
  }

  private boolean checkMainDiag(int c) {
    for (int i = 0; i < boardSize; i++)
      if (board[i][i] != c)
        return false;
    return true;
  }

  private boolean checkOtherDiag(int c) {
    for (int i = 0; i < boardSize; i++)
      if (board[i][boardSize - i - 1] != c)
        return false;
    return true;
  }

  private boolean checkWinnerRow(int row, int c) {
    for (int i = 0; i < boardSize; i++)
      if (board[row][i] != c)
        return false;
    return true;
  }

  private boolean checkWinnerCol(int col, int c) {
    for (int i = 0; i < boardSize; i++)
      if (board[i][col] != c)
        return false;
    return true;
  }